You can have it both ways—don't let anyone tell you otherwise.
1. Have an "off-season" program
To gain some serious size you should have an “off-season” where your goals focus around hypertrophy, and strength gains take a backseat. During this period, focus on high reps, short rest periods, and more isolation movements to hit each muscle. This period should last 12-16 weeks and it should obviously be far away from your next powerlifting competition. Don’t abandon compound movements during this period, but do a higher percentage of assistance work compared to the big three lifts. Our winter bulk up plan is a good examples.
2. Mix powerlifting with bodybuilding
During your powerlifting “season” think of each workout as two separate workouts. The first part will be your big, heavy compound movements. This is the powerlifting influenced part of your workout. We want heavy weights, low reps and longer rest periods. Include 2-3 exercises in this “powerlifting” style. The second part of the workout is the bodybuilding portion. Here you are going to do isolation movements, high reps, and short rest periods. This part of your workout should consist of 5-7 exercises done with short rest periods (60-90 seconds). For a similar styled set of workout routines, check out the monster program.
3. Simplify your nutrition and diet
If you want to be strong and look good your diet has to be on point year round. You don’t need to take it to extremes like a bodybuilder getting ready for a show, but you can’t eat pizza and fried chicken every meal either. The most important part of your diet is to eat at least 1g of protein per pound of bodyweight, preferably more like 1.2-1.5g per pound of bodyweight. If you gain weight easily, watch your carb intake. Eat plenty of fresh vegetables. And lastly, stay away from processed and fried foods as much as possible. Or, reference our how to eat to bulk up guide.